Any clue ? I definitely can't use the UNC path, my hosting provider just confirmed that, therefore I need a way to automate the copy of the images to the db in order of being able to see the images embedded in the old posts.

The image you using as working example is not in app_data folder, image that not working is inside app_data. You need either use folder outside app_data for images or have image path changed from "App_Data/files/2012/2/picBlueTienda.jpg"
to "image.axd?picture=/2012/2/picBlueTienda.jpg".

The PostContent field of table be_posts already shows "image.axd?picture=/2012/2/picBlueTienda.jpg" . Keep in mind that this
post was published under BE 2.0 and it was working fine. I also tried "/blog/es/image.axd?picture=/2012/2/picBlueTienda.jpg", as it was originally, I am in a subfolder, but it didn't work neither (see this
post)

This is not true as the storageVariable provider is set to database, remember I can not use the UNCBlogprovider. The picDiprolab.jpg is stored in the database not in the directory, at least it is what I
think. I saw it in the be_FileStoreFiles table. I do not even have a app_data/files/2012/07 folder

This picture

/blog/es/app_data/files/2012/2/picBlueTienda.jpg

is really stored in that directory. It was published with BE 2.0

I just a published a new post
here and the image does not show up in the app_data directory but it appears just fine on the post

In case you were not aware, there are actually 3 BlogFileSystemProviders.

XmlFileSystemProvider (tied to App_Data, and works the same as BE 2.5, 2.0, 1.6, etc)

DbFileSystemProvider (only works with SQL Server, and not other DB types)

UNCFileSystemProvider (is for storing images/files on the file system, somewhere other than App_Data)

The providers in the web.config file are actually not named very clearly. These 3 providers above can be found in the web.config file:

<add description="Xml Blog Provider" name="XmlBlogProvider" type="BlogEngine.Core.Providers.XmlFileSystemProvider, BlogEngine.Core"/>(the name here is XmlBlogProvider, and would be more clear if named XmlFileSystemProvider")

<add storageVariable="BlogEngine" description="Sql Database Provider" name="DbBlogProvider" type="BlogEngine.Core.Providers.DbFileSystemProvider, BlogEngine.Core"/>(the name here is DbBlogProvider, and would be more clear if named "DbFileSystemProvider")

<add storageVariable="\\UNCPath\BlogFiles" description="UNC Path Provider" name="UNCBlogProvider" type="BlogEngine.Core.Providers.UNCFileSystemProvider, BlogEngine.Core" />(the name here is UNCBlogProvider, and would be more clear if named "UNCFileSystemProvider")

You probably want to use the XmlFileSystemProvider, which was the one that you were using before in BE 2.0. Your images are in the App_Data folder. image.axd will retrieve the images from the App_Data folder if you set your
default blogFileSystemProvider to the XmlFileSystemProvider. In the above example, the name of XmlFileSystemProvider is (confusedly) "XmlBlogProvider". So your web.config file would look like:

<blogFileSystemProviderdefaultProvider="XmlBlogProvider">

If you were using the DbFileSystemProvider when you created
this post, then the Image is probably stored in the be_FileStoreFiles DB table (stored as binary data). I would switch to the XmlFileSystemProvider (aka XmlBlogProvider), and that *should* bring back images from your old posts. Then any
recent posts you made which may have stored the images in be_FileStoreFiles, you'll probably want to re-upload into the recent blog posts, and they should get stored in the App_Data folder instead of the DB.

Btw, I'm assuming you don't mind storing your images in the App_Data folder. If you prefer to store all your images in the DB, then you can use the "change file system provider" tool described below ... which would transfer your existing images in
the App_Data folder into the DB. Unless you have a reason for doing this, I personally think it's preferable to keep the images stored in the App_Data folder.

Change File System Provider - as a sidenote, in the control panel, at the bottom of the Advanced settings page is a File Storage Management section. This area allows you to either backup all your images to a ZIP file, or you can even
switch File Storage Providers. I haven't tested this out, but presume it works. You shouldn't need to use this for your purposes. Just thought I'd point out that this exists.